INTERNATIONAL STANDARD

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1 INTERNATIONAL STANDARD IEC Fourth edition 1974 Basic environmental testing procedures Part 2: Tests Tests B: Dry heat This English-language version is derived from the original bilingual publication by leaving out all French-language pages. Missing page numbers correspond to the Frenchlanguage pages. Reference number IEC :1974(E)

2 INTERNATIONAL STANDARD IEC Fourth edition 1974 Basic environmental testing procedures Part 2: Tests Tests B: Dry heat IEC 1974 Copyright - all rights reserved No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland Telephone: Telefax: inmail@iec.ch Web: Commission Electrotechnique Internationale International Electrotechnical Commission Международная Электротехническая Комиссия PRICE CODE For price, see current catalogue V

3 - 3 - CONTENTS Page r OREWORD 5 PREFACE 5 Historical survey of Test B: D ry heat 7 Relationship of suffixes between Tests A: Cold, and Tests B: Dry heat 9 INTRODUCTION 11 SECTION ONE - TEST Ba: DRY HEAT FOR NON HEAT-DISSIPATING SPECIMEN WITH SUDDEN CHANGE OF TEMPERATURE Clause 1. Scope General description Description of test apparatus Severities Preconditioning Initial measurements Conditioning Intermediate measurements Recovery Final measurements Information to be given in the relevant specification 23 SECTION TWO - TEST Bb: DRY HEAT FOR NON HEAT-DISSIPATING SPECIMEN WITH GRADUAL CHANGE OF TEMPERATURE 12. Scope General description Description of test apparatus Severities Preconditioning Initial measurements Conditioning Intermediate measurements Recovery Final measurements Information to be given in the relevant specification 31 SECTION THREE - TEST Bc: DRY HEAT FOR HEAT-DISSIPATING SPECIMEN WITH SUDDEN CHANGE OF TEMPERATURE 23. Scope General description Description of test apparatus Severities Preconditioning Initial measurements Conditioning Intermediate measurements Recovery Final measurements Information to be given in the relevant specification 43 SECTION FOUR - TEST Bd: DRY HEAT FOR HEAT-DISSIPATING SPECIMEN WITH GRADUAL CHANGE OF TEMPERATURE 34. Scope General description Description of test apparatus Severities Preconditioning Initial measurements Conditioning Intermediate measurements Recovery Final measurements Information to be given in the relevant specification 57 APPENDIX A - Volume of test specimen 59 APPENDIX B - Nomogram for correction for ambient temperature 60 APPENDIX C - Diagrammatic representation of test with forced air circula tion for Method A of Test Bd 62 APPENDIX D - Diagrammatic representation of test with forced air circulation for Test Bc and for Method B of Test Bd 63

4 5 INTERNATIONAL ELECTROTECHNICAL COMMISSION BASIC ENVIRONMENTAL TESTING PROCEDURES Part 2: Tests Tests B: Dry heat FOREWORD 1) The formal decisions or agreements of the IEC on technical matters, prepared by Technical Committees on which all the National Committees having a special interest therein are represented, express, as nearly as possible, an international consensus of opinion on the subjects dealt with. 2) They have the form of recommendations for international use and they are accepted by the National Committees in that sense. 3) In order to promote international unification, the IEC expresses the wish that all National Committees should adopt the text of the IEC recommendation for their national rules in so far as national conditions will permit. Any divergence between the IEC recommendations and the corresponding national rules should, as far as possible, be clearly indicated in the latter. PREFACE This recommendation has been prepared by Sub-Committee 50B, Climatic Tests, of I E C Technical Committee No. 50, Environmental Testing. The present edition consists of the third edition (1966) of Test B: D ry heat, to which have been added Test Bc: Dry heat for heat-dissipating specimen with sudden change of temperature, and Test Bd: D ry heat for heat-dissipating specimen with gradual change of temperature. A first draft was discussed during the meeting held in Washington in As a result of this meeting, a second draft, document 50B(Central Office)159, was submitted to the National Committees for approval under the Six Months' Rule in February Amendments, document 50B(Central Office)168, were submitted to the National Committees for approval under the Two Months' Procedure in July The following countries voted explicitly in favour of publication: Australia Hungary Romania Belgium Italy South Africa (Republic of) Canada Japan Sweden Czechoslovakia Netherlands Switzerland Denmark Norway Turkey Finland Portugal United Kingdom Germany The French National Committee submitted a negative vote which was not due to any disagreement with the technical content of the document, but because they considered that the format of presentation requested by the majority of the National Committees at the meeting of Sub-Committee 50B, in Lenin grad, in 1971, is unduly complicated. The French National Committee requested that this negative vote, and the reason for it, be recorded. The United States National Committee voted for Tests Ba and Bb, but wished it to be recorded that they could not accept Tests Bc and Bd because they preferred to test with forced air circulation. This recommendation should be read in conjunction with IEC Publications 68-1, Basic Environmental Testing Procedures, Part 1, General, and , Basic Environmental Testing Procedures, Part 3, Back ground Information, Section One: Cold and Dry Heat Tests.

5 7 HISTORICAL SURVEY OF TEST B: DRY HEAT First edition (1954) Contained one procedure only Test B: Dry heat, dealing with sudden change of temperature. Second edition (1960) Equivalent to the previous Test B; however, standard test temperature range extended to 200 C. Third edition (1966) Introduced: Test Ba, equivalent to the previous Test B; however, standard test temperature range extended to 1000 C; Test Bb, a new method dealing with gradual change of temperature. Fourth edition (1974) Introduced: Test Ba, equivalent to the previous Test Ba; Test Bb, equivalent to the previous Test Bb; Test Bc, a new method dealing with sudden change of temperature for heat-dissipating specimens; Test Bd, a new method dealing with gradual change of temperature for heat-dissipating specimens. For directly related recommendations, see: Publication 68-1: General. Publication : Background Information. Section One: Cold and Dry Heat Tests.

6 RELATIONSHIP OF SUFFIXES BETWEEN TESTS A : COLD, AND TESTS B: DRY HEAT The relationship of suffixes between Tests A: Cold, and Tests B: Dry heat, is shown in the following table: Tests A: Cold Tests B: Dry heat Suffix letter Specimen Temperature Specimen temperature Specimen Temperature Specimen temperature type change at commencement type change at commencement of test duration of test duration a non heat sudden stabilized* non heat sudden stabilized* b non heat gradual stabilized* non heat gradual stabilized* c heat sudden stabilized* d heat gradual stabilized* heat gradual stabilized* * The specimens will normally reach temperature stability before commencement of test duration. In exceptional cases, this will not be so, and additional information will be required in the relevant specification. See Clause 1 of the Introduction and IEC Publication (Amendments to cover these cases are under consideration.)

7 11 BASIC ENVIRONMENTAL TESTING PROCEDURES Part 2: Tests Tests B: Dry heat INTRODUCTION 1. General This publication deals with dry heat tests applicable both to heat-dissipating and non heatdissipating specimens. For non heat-dissipating specimens, Tests Ba and Bb do not deviate essentially from earlier issues. The object of the dry heat test is limited to the determination of the ability of components, equipment or other articles to be used or stored at high temperature. These dry heat tests do not enable the ability of specimens to withstand or operate during temperature variations to be assessed. In this case, it would be necessary to use Test N: Change of temperature. The dry heat tests are subdivided as follows: Dry heat tests for non heat-dissipating specimens with sudden change of temperature, Ba; with gradual change of temperature, Bb. Dry heat tests for heat-dissipating specimens with sudden change of temperature, Bc; with gradual change of temperature, Bd. The procedures given in this publication are normally intended for specimens which achieve temperature stability during the performance of the test procedure. The duration of the test commences at the time when temperature stability of the specimen has been reached. For the exceptional cases when the specimen does not reach temperature stability during the performance of the test procedure, the duration of the test commences at the time when the test chamber reaches the test temperature. The relevant specification shall define: a) the rate of change of temperature in the test chamber; b) the time at which the specimens are introduced into the test chamber; c) the time at which the exposure commences; d) the time at which the specimens are energized. For these cases, the specification writer will find guidance on choosing the above four parameters in I EC Publication (Amendments to cover these cases are under consideration.)